Agricultural planter's are designed to plant crops such as corn, soybeans, cotton, peanuts and other crops. Modern planters typically are 12 or more rows in width. The overall width of these planters require that they have flexible frames to follow the contours of the ground and to fold for a narrower transport width. The row units on a planter will typically include, among other components, a seed meter. Seed meters perform a central function in the precise placement of seeds in the ground. Precise and accurate seed placement is factor in crop yield which in turn is factor in farm profitability.
Seed meters are usually driven by mechanical or hydraulic-mechanical systems and may include numerous complex drive chains and drive shafts to transmit the power from a central power source to the individual row units. The flexibility and folding features of the planter frame further complicate mechanical power distribution. From a manufacturing perspective, these systems require a significant amount of hand assembly, reducing manufacturing efficiency and increasing planter costs. From a planter performance perspective, these systems have inherent backlash, windup and compliance which manifests in a variability of rotation of the seed meter device and ultimately have a negative influence on seed placement precision and accuracy. With these mechanically driven systems, as planting speed increases, the seed placement accuracy decreases.
Timely planting is also critical to crop yield and farm profitability. A narrow, optimal window for planting occurs each planting season. Paradoxically, while it is important to limit planting speed for proper seed placement, it is equally important to increase planting speed to plant within the optimal time available.
In addition to the seed placement issue, it may also be desirable, for agronomic reasons, to plant individual rows at different rates or variable rates. To accomplish variable rate planting at each row using a centralized mechanical or hydro-mechanical power source becomes very complex and impractical. At best, variable rate drive systems are practical in multiple row sections, not at the individual row unit. To be practical, a variable rate or individual row unit rate adjustment must be possible on-the-go, that is, while the planter is in operation.
Some crops are planted in twin rows in which the seeds are planted in pairs of rows spaced relatively close together with larger spaces between the pairs. Because of the narrow spacing of the twin rows, the twin row units are spaced fore and aft where one of the twins is placed ahead of the other twin relative to the planter frame. Agronomically, because of the narrow spacing between the twins, it is desired to stagger or synchronize the placement of the seeds in the twin pair. Seed meter synchronization is a function of population. That is, as the population changes, the synchronization relationship between the twin meters also changes. On a mechanically driven system, the synchronization relationship is changed by mechanically adjusting the twin meters relative to on another. To adjust the twin rows on-the-go is extremely complex and impractical. The current method is to stop planting and manually adjust one or both seed meters of each twin pair.
Crop input costs also affect farm profitability. As input costs increase, and as farm sizes increase, the economic impact of waste becomes significant. Seed costs are an example of inputs that continue to rise. With planters, seed waste occurs due to spilling seed on the ground when filling the meter seed disks prior to planting, overshooting the target population when starting the meters, delay in stopping the meters and overplanting in areas of lower population. Similarly, cropland is not fully utilized if there are skips in the field where seed is under-planted or simply not planted. Mechanical or hydro-mechanically driven systems can be identified as a cause of these wastes.
Electric driven seed meter can be useful in overcoming some of the above problems. An example of such a drive is seen in U.S. Pat. No. 4,928,607. Another example is WO 2008/135772 which shows individual row units with their respective row unit motor controller and a master controller. These give independent control of the motors as shown in U.S. Pat. No. 7,395,769.